P-D-Galactopyranose

Fig. 9. Partial structural formulas and shorthand notations for principal hemiceUuloses found in wood, where the sugar units ate noted as P-D-xylopyranose (Xylp), 4-Omethyl-a-D-glucopyranosyluronic acid (GlupU), a-L-arabinofuranose (Araf), P-D-glucopyranose (Glup), P-D-mannopyranose (Manp), and P-D-galactopyranose (Galp) for (a) arabino-4-O-methylglucuronoxylan from softwood, (b) 0-acetyl-galactoglucomannan from softwood, and...

Galactose differs from glucose in configuration at C-4. The C-4 hydroxyl is axial in p-D-galactopyranose, but it is equatorial in p-o-glucopyranose. ... 

Deoxy-p-D-xy/o-hexopyranose 2-Deoxy-D-ribo-hexose not 2-deoxy-D-allose not 4-deoxy-p-D-galactopyranose... 

A satisfactory result was obtained in AgOTf- or NIS/TfOH-activated condensation of S-benzothiazolyl pentofuranosides 93, 94 and 95 with l,2 3,4-di-isopropylidene-a-D-galactopyranose 96 and l,6-anhydro-3,4-isopropylidene-P-D-galactopyranose 97 as the acceptor to afford the corresponding disaccharides in moderate to good yields and stereoselectivity [445],... 

An alternative approach, in which the anomeric centre of the sugar is reacted with a carbon nucleophile, but the amino group is subsequently inserted at the other side or in both sides at the same time, is reported in Fig. 41 for the synthesis of a- and (3-homogalactonojirimycin.72 Reaction of 2,3,4,6-tetra-O-benzyl-p-D-galactopyranose with methylenetriphenylphosphorane generated an enitol on which the amino group was inserted as phtalimide by a double inversion process of the 5-OH, under Mitsunobu s conditions. 

Auch eine direkte Substitution der Mesyl-Gruppe in 2-0-Methansul-fonyl-3,4-0-isopropyliden-l,6-anhydro-p-D-galactopyranose mit KF in... 

Die in der Zuckerchemie iibliche Methode der Substitution einer Mesyloxy-Gruppe unter Waldenscher Umkehr wurde zur Darstellung der 2-Amino-2-desoxy-l,6-anhydro-p-D-gulopyranose aus dem 3-mesylierten Derivat der 2-Acetamido-2-desoxy-l,6-anhydro-p-D-galactopyranose aus-gentitzt... 

Femer wurde 1,6-2,3-Dianhydro-p-D-talopyranose durch alkalische Hydrolyse des Bariumsalzes des l,6-Anhydro-p-D-galactopyranose-2-sulfats gewonnen... 

Aufspaltungen der Epoxide mit Sauren fiihren zu neuen interessanten Derivaten so wurde aus 2-0-p-Toluolsulfonyl-l,6-3,4-dianhydro-p-D-galactopyranose die 2-0-p-Toluolsulfonyl-l,6-anhydro-p-D-glucop)Tanose erhalten Bei gleichzeitiger Anwesenheit von Alkoholen entstehen die entsprechenden 4-0-Alkyl-Derivate 28,32) ... 

Formation of l,2 5,6-di-0-isopropylidene-a-D-n7i( -hexo-furanos-3-ulose (Fig. 2.13, 2.4.2.1 Table 2.3) was one of the first carbohydrate oxidations effected by stoich. RuOyCCl [310, 311]. The reagent was also used for oxidation of 1,6-anhydro-3,4-0-isopropylidene-P-D-galactopyranose to the -P-D-/yxo-hexopyranos-2--ulose, part of a route leading to 1,6-anhydro-P-D-talopyranose (Fig. 2.15) [321]. 

To a solution of 2-(trimethylsilyl)ethyl CMmethyl 5-acetamido-4,7,8,9-tetra-0-acetyl-3,5-dideoxy-D-g/ycero-a-D-galacto-2-nonulopyranosylonate)-(2->3)-2,4,6-tri-0-benzoyl-P-D-galactopyranose (295 mg, 0.28 mmol) in 2 mL of dichloromethane was added trifluoro-acetic acid (2 mL) at 0°C, and the stirring was continued for 2 h at 0°C. Ethyl acetate (3 mL) and toluene (3 ml) were added and the solvents were evaporated. A second portion of toluene was added and the evaporation was repeated. Purification by flash chromatography on silica gel column with dichloromethane-methanol (20 1) gave the hemiacetal 21 (267 mg, quantitative) mp 85°C. 

SAMPLE SOLUTION (a) By analogy with the procedure outlined for D-glucose in Figure 25.4, first generate a Haworth formula for p-D-galactopyranose ... 

Sodium hydroxide-induced partial allylation was used for preferential reaction at the equatorial OH-4 in l,6-anhydro-2-0-benzyl-P-D-galactopyranose [229]. A similar reaction of allyl 2,6-di-O-benzyl-a-D-galactopyranoside with allyl bromide and sodium hydroxide in benzene at room temperature was not as regioselective, the per-substituted 3,4-di-O-allyl derivative dominated in the reaction product [73]. A high, 87 % yield of the monoallyl derivative was obtained from 1,2 5,6-di-O-isopropylidene-D-mannitol after the treatment with allyl bromide and sodium hydroxide in aqueous acetone [230],... 

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